Factoring Site Age in Evaluation of Groundwater-Contamination Hazard Rating of Abandoned Municipal Solid-Waste Landfill Sites

A time-dependent system for evaluating the groundwater-contamination hazard rating of uncontrolled municipal solid-waste landfills has been reported elsewhere. While prioritizing uncontrolled landfills for remedial actions, this system (TD-HARAS) accords equal importance to the groundwater contamination caused by a landfill in the past and the contamination to be caused in the future. Some policymakers may like to remediate first those landfills that have greater potential for future contamination; landfill age then becomes an important factor to be taken into consideration for landfill prioritization. In this note, the mathematical framework of TD-HARAS has been extended to allow differential importance to past and future contaminations and to incorporate site age in the assessment of the groundwater-contamination hazard rating of landfill sites. A sensitivity analysis of the extended system (ETD-HARAS) shows that the groundwater-contamination hazard rating of a landfill site decreases with increases in the site age. A comparison of ETD-HARAS with selected existing hazard-rating systems shows that although ETD-HARAS produces significantly differing scores for different landfills and thus responds to varied site conditions, the existing systems individually produce clustered scores and return the same rank to more than one landfill. Thus, ETD-HARAS makes a better basis for site prioritization for taking remedial actions.